1. Field of the Invention
The present invention relates to an object reflector detecting apparatus for determining the position of markings or installations by emitting a light from a polarized light source and then by detecting a specified reflector.
2. Description of Background Art
The object reflector detecting apparatus has been used for determining the height level in the works of the civil engineering or the architecture.
Recently, a semiconductor visible laser has been put to practical use and thus an object reflector detecting apparatus using the semiconductor visible laser has been developed. However, the output of the semiconductor visible laser is limited in view of safety of a worker and therefore the measurement accompanied with confirmation by visual observation is limited within a relatively short working distance.
Japanese Patent Application No. 289042/1992 filed on Oct. 27, 1992 discloses a rotary laser irradiating apparatus in which the position of a specified reflector arranged at a predetermined position is reciprocally scanned by a laser beam in order to extend the working distance.
In the rotary laser irradiating apparatus disclosed in Japanese Patent Application No. 289042/1992, a specified pattern is formed on the reflector in order to surely detect the object reflector.
However, since the object reflector detecting apparatus is used in various places, it is impossible to discriminate if the reflected signal pattern is that from the object reflector or from a non-object reflector and therefore it is difficult to perfectly exactly identify the object reflector and the non-object reflector and thus a scanning operation would be sometimes caused at an erroneous position.
Especially, when the laser beam from the rotary laser irradiating apparatus perpendicularly strike a non-object reflector having a reflecting surface such as a glittering member, the incident optical axis and the reflection optical axis correspond with each other and thus an intensive reflected light (hereinafter referred to "regular reflection light") enters into a detecting section of the apparatus. Accordingly, when the regular reflection light would take an arrangement similar to that of the predetermined pattern signal, the scanning error will be caused although the distance between the apparatus and the non-object reflector is long.
In addition, when there is any glitter flat member such as a glass plate near a working site, an other optical path would be sometimes formed between the apparatus and the specified reflector. In such a case, there is a problem that an erroneous scanning operation would be caused to the virtual image of the glitter member by detecting a reflected light (hereinafter referred to "multiple reflection light") of said other optical path.